Mold on once-turned bowls

[Holmes Anderson]

I have been making some once-turned bowls from a cherry tree that was dormant and healthy when cut. Mold spots form on the bowls within about 24-48 hours of turning. Not sure about the MC but it is probably high because the wood has been in below freezing temps and is being turned while still frozen so most of the moisture that was in the standing tree is basically locked in until the bowls warm up during drying. The shop temp is about 50 degrees F and the RH is usually low. The mold spots are troublesome because they run too deep to easily be sanded away. Not sure what would be the simplest solution. Basic kiln? Bleach or boric acid wash? Just rough-turn and deal with the mold later during a second turning?

Bowls being dried on a shelf 15 feet from an exterior door without anything to slow drying. Mold forms even if they are not stacked. Very little mold forms on rough-outs sealed with Anchorseal and stacked nearby so I assume the mold spores are in the shop.

 

[Don Wattenhofer]

I have done many pieces from green cherry and have never had a problem like that and since I detest drying checks in a turned piece I try to turn as soon as possible. When I do a once turned piece I always try for as consistently thin wall as possible and they will then dry within a few days. The bowl in the picture shows what you can do if you get it thin enough such that it will distort rather then crack. My shop is kept at least 50 degrees F and when I am in there towork I fire up a wood burning stove and bring it up to about 65 to 68 F.

 

[Randy Anderson]

Holmes, I've turned a lot of black Cherry but don't recall mold spots being an issue on once turned or twice turned. You have any pics to share? You sure they're not metal stain spots from your tools?

 

[Holmes Anderson]

 

[Randy Anderson]

Not sure but that could well be metal staining. Certainly looks like it in the circle where your live center was in place. Have you doused it good with lemon juice? I often spray entire pieces down if I start to see any signs of it. Rub it on, all around, let it sit, spray some more, etc. Miracle solution to the problem if that's what it is. I spray my hands as well after turning walnut and other woods that stain my hands.

 

[hockenbery]

I usually rinse my once turned bowls in the sink before I start to dry them
It adds some moisture back to the endgrain and gets any dust off the bowl

 

[robo hippy]

I am wondering if those are metal stains rather than mold. I learned long ago to wipe off my tools after sharpening, and my hands, before going back to the wood. Any metal dust on hands and/or tool will cause spots and finger prints. concentrated lemon juice removes them instantly when the wood is still fresh. Much slower when the wood has dried, which takes a week at most in my shop.

robo hippy

 

[Holmes Anderson]

Thanks, I will try the lemon juice. I would much rather it is metal stains than mold. I think some of the marks even look suspiciously like fingerprints.

 

[Brian Gustin]

Agree with the others - Looks like Tannins in the wood reacting with iron/metal (Oak will do that too) Do you happen to be sharpening tools on grinder nearby? Dust from grinding can get in the air and settle on the wood , resulting in stains like that. It isn't just metal either- you can get that black staining from sweating on even dry wood (salts and minerals in sweat will also react with the Tannins in the wood)